This invention, in one aspect, relates to dosage forms and methods for ameliorating erectile dysfunction in psychogenic male patients. In another aspect this invention relates to diagnosis of erectile dysfunction. More particularly, this invention relates to the use of apomorphine-containing compositions for amelioration of erectile dysfunction in male patients and for diagnostic purposes.
A normal erection occurs as a result of a coordinated vascular event in the penis. This is usually triggered neurally and consists of vasodilation and smooth muscle relaxation in the penis and its supplying arterial vessels. Arterial inflow causes enlargement of the substance of the corpora cavernosa. Venous outflow is trapped by this enlargement, permitting sustained high blood pressures in the penis sufficient to cause rigidity. Muscles in the perineum also assist in creating and maintaining penile rigidity. Erection may be induced centrally in the nervous system by sexual thoughts or fantasy, and is usually reinforced locally by reflex mechanisms. Erectile mechanics are substantially similar in the female for the clitoris.
Impotence or male erectile dysfunction is defined as the inability to achieve and sustain an erection sufficient for intercourse. Impotence in any given case can result from psychological disturbances (psychogenic), from physiological abnormalities in general (organic), from neurological disturbances (neurogenic), hormonal deficiencies (endocrine) or from a combination of the foregoing.
These descriptions are not exact, however. There is currently no standardized method of diagnosis or treatment. As used herein, psychogenic impotence is defined as functional impotence with no apparent overwhelming organic basis. It may be characterized by an ability to have an erection in response to some stimuli (e.g., masturbation, spontaneous nocturnal, spontaneous early morning, video erotica, etc.) but not others (e.g., partner or spousal attention).
Various methods for the treatment of impotence have been suggested, including external devices, for example, tourniquets (see U.S. Pat. No. 2,818,855). In addition, penile implants, such as hinged or solid rods and inflatable, spring driven or hydraulic models, have been used for some time. The administration of erection effecting and enhancing drugs is taught in U.S. Pat. No. 4,127,118 to LaTorre. That patent teaches a method of treating male impotence by injecting into the penis an appropriate vasodilator, in particular, an adrenergic blocking agent or a smooth muscle relaxant to effect and enhance an erection. More recently, U.S. Pat. No. 4,801,587 to Voss et al. teaches the application of an ointment to relieve impotence. The ointment consists of the vasodilators papaverine, hydralazine, sodium nitroprusside, phenoxybenzamine, or phentolamine and a carrier to assist absorption of the primary agent through the skin. U.S. Pat. No. 5,256,652 to El-Rashidy teaches the use of an aqueous topical composition of a vasodilator such as papaverine together with hydroxypropyl-xcex2-cyclodextrin.
Recently the effect of apomorphine on penile tumescence in male patients afflicted with psychogenic impotence has been studied. These studies show that while apomorphine can indeed induce an erection in a psychogenic male patient, the apomorphine dose required to achieve a significant erectile response is usually accompanied by nausea or other serious undesirable side effects such as hypertension, flushing and diaphoresis. The specific mechanisms by which apomorphine acts to produce an erectile response in a human patient are not yet completely understood, however.
Moreover, apomorphine has been shown to have very poor oral bioavailability. See, for example, Baldessarini et al., in Gessa et al., eds., Apomorphine and Other Dopaminomimetics, Basic Pharmacology, Vol. 1, Raven Press, N.Y. (1981), pp. 219-228.
Thus the search is continuing for an effective treatment of psychogenic impotence in male patients as well as for diagnostic methods that can identify such patients. It has now been found that certain delivery systems for apomorphine can provide a practical therapeutic and/or diagnostic xe2x80x9cwindowxe2x80x9d while reducing the likelihood of undesirable side effects. It has also been found that nausea side effects associated with the use of apomorphine can be substantially reduced by the pre-administration or co-administration of an antiemetic agent.
It has now been found that, for an optimal erectile response, steady state circulating serum and mid-brain tissue levels of apomorphine are to be maintained within a relatively closely defined range.
Nasal spray apomorphine dosage forms, usually containing about 1 to about 3 milligrams of apomorphine, are effective in male patients suffering from erectile dysfunction for the induction and maintenance of an erection sufficient for intercourse (i.e., vaginal penetration) without nausea or other undesirable side effects. The apomorphine is administered intranasally, preferably about 15 to about 20 minutes prior to sexual activity, and so as to maintain a predetermined circulating serum levels and mid-brain tissue levels of apomorphine during the period of sexual activity sufficient to induce an erection adequate for vaginal penetration but less than the amount that induces nausea. The plasma concentration of apomorphine should be maintained at no more than about 5.5 nanograms per milliliter, preferably about 0.3 to about 4 nanograms per milliliter, and more preferably about 1 to about 2 nanograms per milliliter.
The foregoing intranasal apomorphine dosage forms are also suitable for screening patients complaining of erectile dysfunction.
The nausea side effect associated with the use of apomorphine can be substantially reduced by administration of an antiemetic agent together with the apomorphine. Specifically, a method suitable for treating erectile dysfunction in a male patient comprises administering to the patient prior to sexual activity, an antiemetic agent in an amount sufficient to substantially reduce nausea associated with use of apomorphine, and apomorphine in an amount sufficient to induce and maintain an erection adequate for vaginal penetration.
The antiemetic agent is preferably co-administered with the apomorphine in a single nasal spray dosage unit. Separate dosage units with differing delivery routes are also suitable for practicing the present invention, however. For example, the antiemetic agent and apomorphine may be administered to the patient sequentially by first administering a composition comprising an antiemetic agent by any desired route of administration and thereafter a nasal spray composition comprising apomorphine.
A nasal spray dosage form for administering the antiemetic-apomorphine combination comprises apomorphine, an antioxidant, and optionally an antiemetic agent, in an aqueous pharmacologically acceptable liquid vehicle. The preferred anti-emetic agent is domperidone.